Armadale detectives have charged a teenager with grievous bodily harm over an incident in which a 18-year-old man was stabbed at a party in Piara Waters in September.
Police were called to the Southampton Drive home after an out of control party spilled out onto the street.
They found an 18-year-old with a stab-wound to his abdomen and suffering serious internal injuries.
He was treated at Royal Perth Hospital, where he remained for a week.
A 16-year-old Wannanup boy was arrested in Mandurah yesterday and charged with grevious bodily harm.
He is due to appear in the Armadale Magistrate's Court on Monday 26 November.